ISSUE-266: add ability for instance documents to declare what profile(s) it conforms to

add ability for instance documents to declare what profile(s) it conforms to

TTML1 SE defines a profile mechanism to signal to a presentation engine the required set of TTML features to properly present the document, suggesting strongly that documents should otherwise be rejected.

It would be useful to be able to use this same basic mechanism to signal what profile(s) instance documents conform to.

EBU liaison has requested feature to allow document conformance to (zero to many) profiles to be described using short form aliases to allow references to specifications not wholly defined by schemas or feature designators, i.e. where behaviour is described normatively in documentation.

Nigel Megitt, 23 Oct 2013, 14:02:13

[pal]: add ability for instance documents to declare what profile(s) it conforms to